Democratic Candidate Hillary Clinton’s plan to “staple” a green card to the diplomas of foreign students graduating with masters and PhDs in the Science, Technology, Education, and Mathematics fields would hurt the job prospects and wages of American graduates already struggling in a glutted labor market, according to Sen. Jeff Sessions (R-AL).

“Although there are more college graduates in the U.S. today than at any point in our history, many have trouble finding meaningful work in their field of study. Many are underemployed, taking jobs well below their skill level simply to make ends meet,” Sessions, a policy adviser to Clinton’s presumptive Republican opponent Donald Trump, said in a statement. He noted that among STEM graduates some 74 percent are already not working in STEM fields.

Clinton unveiled her plan to keep America on the vanguard of technology and innovation on Tuesday. If elected president, part of her plan includes a promise to “‘staple’ a green card to STEM masters and PhDs from accredited institutions—enabling international students who complete degrees in these fields to move to green card status,” allowing foreign students to stay and work in the U.S. as lawful permanent residents.

Sessions argues Clinton’s plan is a rehashing of what the “industry-backed” advocates seeking lower priced labor have dubbed “immigration reform.” In the end, the Alabama lawmaker charges, the plan would largely serve to hurt Americans.

He cited the work of Ron Hira, Paula Stephan, Hal Salzman, Michael Teitelbaum, and Norm Matloff, a group of professors and researchers who have conducted research on the impact of immigration on STEM jobs and wages in the U.S. They concluded in a joint op-ed that “there is an ample supply of American workers (native and immigrant, citizen and permanent resident) who are willing and qualified to fill the high-skill jobs in this country” and that they have been unable to find “any credible evidence” of a labor shortage.

“The only real disagreement is whether supply is two or three times larger than the demand,” Sessions quoted from the op-ed, pointing to two additional points.

1. The industry-backed concept of ‘stapling a green card’ to a diploma ignores the fact that the ‘“stay rates” for visiting international students are very high and have shown no sign of decline.’

2. The industry-backed concept of ‘stapling a green card’ to a diploma is driven by the industry’s ‘desire for cheap, young and immobile labor.’

According to Sessions, the stapled green card concept also places American universities in the position of essentially “selling green cards to foreign students,” as Hira once testified before Sessions’ immigration and national interest subcommittee. The impact, Sessions argues, will cause “a flood of foreign students and crowding out American students.”

“Further saturating the STEM labor market will limit [American STEM graduates’] ability to obtain high-paying jobs that will allow them to pay down their debt and pursue the occupation of their choosing,” he said.

Sessions concluded, “Undoubtedly, increasing high-skilled over low-skilled immigration will better serve the national interest. But there must be some limit to all categories of immigration – including high-skilled immigration. Mrs. Clinton’s industry-backed proposal is excessive, and will surely cause damage to the wages and job prospects of many young Americans.”